Since efficiency improvements may be viewed as a form of technical change that both reduces the effective cost of energy services and stimulates economic activity, energy demand may, under some circumstances ,rise even as energy productivity improves. This paper examines this hypothesis using a simple model that distinguishes the roles of energy and energy services in production activities. This paper considers a model of economicgrowth where improvements in energy efficiencyconstitute a form of technicalchange that stimulates increased levels of capitalinvestment and economic activity. The model examined here include energy services, notenergy per se, in the aggregate productionfunction. A structure is specified in which energyservices are produced using both energyand non-energy inputs like capital stock. In this model, improvedenergy efficiency entails increased energyuse only if (i) energy accounts for a largefraction of the total cost of energy services and(ii) the production of energy services constitutes a substantial fraction of economic activity. The theoretical model examined in this paper employs a number of simplifying assumptions that might be generalized in future research. The model’s focus on the Cobb-Douglas production function, where the elasticity of substitution between energy services and other inputs is set equal to one, constitutes something of a special case. The Cobb-Douglas functional form is useful because it permits the analysis of closed-form solutions to the model. Relaxing this assumption is unlikely to affect the insights that emerge by developing the distinction between energy use and energy services. According to the model justified for Iran , improvements in energy will cause a net increase in energy use and economic activity. Additionally , changes in the cost of energy services have identical impacts on capital accumulation and long run economic growth. Changes in unit cost will have major impacts on aggregate economic activity if energy services constitute a large share of gross output.